[900] ERG Expression in Mucinous Prostatic Adenocarcinoma and Prostatic Adenocarcinoma with Mucinous Features: Comparison with Conventional Prostatic Adenocarcinoma

Hunter Johnson, Ming Zhou, Adeboye O Osunkoya. Emory University School of Medicine, Atlanta; Cleveland Clinic Foundation, Cleveland

Background: TMPRSS2-ERG is the most common gene fusion in conventional prostatic adenocarcinoma, identified in about 40-70% of cases. ERG expression detected by rabbit anti-ERG monoclonal antibody has recently been utilized in predicting ERG rearrangement as assessed by FISH in needle core and radical prostatectomy specimens of patients with conventional prostatic adenocarcinoma. Mucinous prostatic adenocarcinomas and prostatic adenocarcinoma with mucinous features are rare subtypes of prostate cancer and ERG expression in these subtypes have not been well characterized in a large series.
Design: A search was made through the surgical pathology files of two major academic institutions for cases of mucinous prostatic adenocarcinoma and prostatic adenocarcinoma with mucinous features. The former were obtained from radical prostatectomy cases and the latter from radical prostatectomy cases, transurethral resection of the prostate and prostate needle core biopsies. A TMA composed of additional cases of mucinous prostatic adenocarcinoma was also included in the study. Immunohistochemical stains for ERG were performed on all the cases.
Results: 51 cases of mucinous prostatic adenocarcinoma and prostatic adenocarcinoma with mucinous features were identified. 25/51 (47%) cases were positive for ERG, including 10/24(42%) radical prostatectomy specimens, 7/14 (50%) biopsies, 2/4 (50%) transurethral resection of the prostate specimens, 6/9 (67%) from the TMA. In all cases of mucinous prostatic adenocarcinoma and prostatic adenocarcinoma with mucinous features that were positive for ERG, and had adjacent usual type adenocarcinoma on the same slide, there was identical expression of ERG in the latter component with the exception of one case.
Conclusions: This is the largest study to date specifically characterizing ERG expression in mucinous prostatic adenocarcinoma and prostatic adenocarcinoma with mucinous features. ERG was expressed in almost 50% of cases of mucinous prostatic adenocarcinoma and prostatic adenocarcinoma with mucinous features in our study, similar to known rates of ERG expression in conventional prostatic adenocarcinoma. In view of the identical expression of ERG in mucinous prostatic adenocarcinoma, prostatic adenocarcinoma with mucinous features, and adjacent conventional prostatic adenocarcinoma in the vast majority of cases, this study confirms that these rare subtypes of prostatic adenocarcinoma are clonally similar to conventional prostatic adenocarcinoma.
Category: Genitourinary (including renal tumors)

Monday, March 19, 2012 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 130, Monday Morning

 

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